A small thatch of hair (approximately 20 strands) will be collected from 85 participants who are currently taking antiretrovirals (ARVs). Hair collection will be evenly distributed into color cohorts: Black, Brown, Blonde and Grey. Participants will need to be >80% adherent to their medication and have had an undetectable HIV RNA VL within the previous 6 months. In the lab, samples will be used to develop IR-MALDESI MSI hair protocols for high sensitivity and accuracy to quantify ARVs in 5 therapeutic drug classes (Integrase Inhibitors, Nucleoside Reverse Transcriptase Inhibitors, Non-Nucleoside Reverse Transcriptase Inhibitors, Entry Inhibitors, Protease Inhibitors).